Yeah I thought it was all a bunch of huey, until I got an 8x10 print back from the lab that clearly showed the negative had "popped: warped in the enlarger from heat and gone out of focus. He reprinted it with a glass neg holder and the image didn't change.

That's when I knew there was some truth to film flatness. It was shot with an XLSW (47mm SA) at f8_________________"In order to invent, you need a good imagination and a lot of junk" Thomas Edison

will the film flatness its just what you get some good & some not so good

But you can look & see by putting in a roll of junk film get it ready to shot
take out the drakslide & look ! NOW if it looks like that the film touckes
tight all the way around the film gate you should be OK! if it don't then a
know that you mite have some problems!! But that can some times it can
be fixed. Some have added a felted backing on the presser plate to take
care of it . ?? I have never tryed this but have been told that it works but
it makes your film a bit roll harder !!